Grinding machine for sharpening the cutting edges of a tool

ABSTRACT

There is described a machine for automatically sharpening the carbide tips of roof drill bits as used in the coal mining industry. Each drill bit is held under constant fluid pressure against a grinding wheel while traversing the face of the wheel a number of times; is then retracted; rotated through 180*; and again pressed against the wheel while traversing the face of the wheel a number of times until the two cutting edges of the drill bit are symmetrical, whereupon the bit is retracted.

United States Patent [191 Sollami [451 Sept. 16, 1975 GRINDING MACHINE FOR S I v ENING THE CUTTING EDGES OF A TOOL [76] Inventor: Phillip A. Sollami, 438 Sherman St.,

Downers Grove, 111. 60515 [22] Filed: June 27, 1974 [21] App]. No.: 483,531

[52] US. Cl. 51/92 BS; 5l/219 R; 51/233 [51] Int. Cl. B24B 3/33 [58] Field of Search 51/92 R, 92 BS, 92 ND,

51/216 ND, 219 R, 231, 233,165.9

[56] References Cited UNITED STATES PATENTS 2,536,823 1/1951 Smith 51/92 ND 2,740,236 4/1956 Flygare 51 92 ND 2,746,212 5/1956 .lensch 51/92 R 3,665,647 5/1972 Weatherell 5l/165.9 x

3,717,960 2/1973 Kuniholm 5l/165.9

Primary Examiner-Al Lawrence Smith Assistant ExaminerNicholas P. Godici Attorney, Agent, or Firm-Edmond T. Patnaude [5 7] STRACT There is described a machine for automatically sharpening the carbide tips of roof drill bits as used in the coal mining industry. Each drill bit is held under constant fluid pressure against a grinding wheel while traversing the face of the wheel a number of times; is then retracted; rotated through 180; and again pressed against the wheel while traversing the face of the wheel a number of times until the two cutting edges of the drill bit are symmetrical, whereupon the bit is retracted.

10 Claims, 5 Drawing Figures SEEET 2 UF 3 PATENTEU SEP 1 6 I975 1 GRINDING MACHINE FOR SI-IARPENING THE CUTTING EDGES OF A TOOL The present invention relates in general to the art of grinding, and it relates more particularly to a new and improved grinding machine which may be used for automatically sharpening roof drill bits as used in the coal mining industry.

BACKGROUND OF THE INVENTION Roof bits as used for drilling in the coal mining industry comprises a carbide cutting tip mounted in a steel carrier. Thesebits, which are used in large numbers, have two cutting edges which must be frequently sharpened, and at the present time this is accomplished by a manual operation performed on an abrasive grinding wheel. Then ground manually the bits lack uniformity so that more frequent sharpening is necessitated and reduced bit life results. Moreover, any excessive grinding also reduces wheel life. Furthermore, the manual sharpening operation is tedious and relatively slow, a good operator being able to sharpen only about 600 roof bits in an eight hour work day.

OBJECTS OF THE INVENTION Therefore, an object of the present invention is to provide a new and improved grinding machine suitable for use in automatically sharpening the cutting edges of roof drill bits.

Another object of this invention is to provide new and improved means for controllably moving a work piece having multiple cutting edges against a grinding wheel in a metal removal operation.

SUMMARY OF THE INVENTION Briefly, the above and further objects may be realized in accordance with the teachings of the present invention by means of a machine which controllably moves a tool piece such as a roof drill bit across the work surface of a rotating grinding wheel to grind a first side of the bit defining one cutting edge on the tool piece, then retracts and rotates the tool piece before again moving it across said work surface to sharpen a second side of the bit defining the second cutting edge thereon. In accordance with a further feature of the invention means are incorporated in the machine to terminate the second sharpening operation when the second side has been ground to an extent whereby it is symmetrical to the first side thereby to provide symmetrical cutting edges on the bit.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages and a better understanding of the present invention can be had by reference to the following detailed description, wherein FIG. 1 is a perspective view of an automatic roof drill bit grinding machine embodying the present invention;

FIG. 2 is a side elevational view, partially in crosssection, of the machine of FIG. 1;

FIG. 3 is a sectional view'taken along the line 33 of FIG. 2;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 3; and

FIG. 5 is a schematic circuit diagram of the electric control system for the machine of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings and particularly to FIG. 1 thereof, the grinding machine 10 embodying the present invention includes a cabinet base 11 having a pedestal 12 near the rear on which is mounted a grinding wheel drive motor 13. A pair of grinding wheels 14 and 15 are respectively mounted to opposite end portions of the shaft of the motor 13, and a manual switch 16 is provided for starting and stopping the motor 13. The grinding wheel 14 is adapted to be used for manual grinding operations as, for example, to grind the steel carrier portion of a carbide roof drill bit. A carriage assembly 18 is mounted, as more fully described hereinafter, for reciprocable movement in a forward and rearward direction toward and away from the wheel 15. A traversing unit 19 is mounted on the carriage assembly and includes an electric drive motor 20 which causes a tool holder support post 22 to traverse back and forth along a path parallel to the shaft of the motor 13 and of the grinding wheel 15. A tool piece holder 23 is mounted to the post 22 and supports a tool piece 24, such as a roof drill bit, in fixed relationship therewith. A tool holder includes a pneumatically operated rotary drive mechanism which is adapted to hold the tool piece 24 in each of two angular positions displaced apart. The entire carriage assembly 18 is reciprocated towards and away from the grinding position by means of a fluid operated cylinder and piston assembly 25 mounted between the top of the cabinet 11 and the base of the carriage. Two electric control switch boxes 27 and 28 are mounted on the top of the cabinet 11 at each side of the machine near the front thereof for controlling the operation of the machine.

Particularly referring to FIGS. 2 and 3, a set of ways comprising a pair of guide rods 30 and 31 are mounted in fixed parallel relationship by means of two pairs of pillow blocks 33 respectively mounted in front and rear positions by T-bolts 35 in T-slots 35a in a plurality of support blocks 34 secured to the top of the cabinet 11. The carriage assembly 18 is slidably mounted to the guide rods 30 and 31 by means of a plurality of bearing blocks 36 bolted to the carriage assembly and including ball bearings which receive the rods 30 and 31. Lateral adjustment of the guide rods 30 and 31 is provided by means of a pair of adjustment screws 37 threadedly mounted in respective ones of a pair of blocks 38 secured as by bolts to the forward blocks 34. The screws 37 extend through openings in a pair of dust covers 39 into engagement with the base flanges of the forward pillow blocks 33. By loosening one of the screws 37 and tightening the other lateral movement of the bit 24 is effected. This adjustment is used to provide uniform wear across the working surface of the wheel 15.

The piston and cylinder assembly 25 is located beneath the carriage between the guide rods 30 and 31 so that when fluid under pressure is supplied to the back of the cylinder 25 (front of the machine) the piston moves rearwardly to move the entire carriage assembly towards the grinding wheel 15. Preferably, the piston and cylinder 25 is pneumatically driven for the necessary high speed operation.

The traversing unit 19 comprises a pair of pillow blocks 40 and 41 which support a plurality of bushings 42, 43, 44 and 45. The bushings 42 and 43 are supported in mutually aligned relationship as are the bushings 44 and 45. A pair of rods 46 and 47 are mounted in fixed parallel relationship in the bearing sets 42, 43, 44 and 45 respectively and are fixedly connected at the respective center portions thereof to a traversing carriage 49 from which the post 22 extends. A drive member 51 having a vertical channel groove 52 therein is fixedly mounted as by bolts to a pair of arms 53 and 54 on the traversing carriage 49 and a roller 57 is disposed to the channel 52. The roller 57 is connected to a crank arm 55 which is rotatably driven by the output shaft 56 of the electric motor 20. The arms 53 and 54 of the traversing unit respectively extend through mutually parallel horizontal slots 58 and 59 in a vertical mounting plate 60 to which the pillow blocks 40 and 41 are mounted. The upper end of the traversing carriage 49 extends through a slot 62 in the top wall 63 of the traversing unit 19 so that when the motor 20 is energized the traversing carriage 49 and the shafts 46 and 47 to which it is fixedly connected reciprocate within the bearings 42-45 causing the tool holder support post 22 to reciprocate in a direction perpendicular to the direction of movement of the carriage assembly 18 on the rods 30 and 31. A dust shield assembly 65 is mounted over the slot 62 to prevent dust and other small particles from entering into the traversing unit 19.

The tool holder assembly 23 is preferably of the type disclosed in US. Pat. 3,128,679 having a pneumatic inlet and outlet connectors 67 and 68 at the top. A shaft 69 in the unit 23 is rotatable against one or another of a pair of fixed stop members within the unit when pressurized air is applied to one or the other of the ports 67 and 68. The stop members are set at 180 apart and as described more fully hereinafter, the shaft is held under pneumatic pressure against one or the other of the stops depending upon which of the inlet ports is supplied with pressurized air during the grinding operation of one of the cutting edges of the carbide bit. A suitable collet 70 is connected to one end of the shaft 69 and is adapted to receive the shank portion 72 of a drill bit 24 mounted therein. The collet 70 may be of the type shown in FIG. 2 including a plurality of set screws 73 and 74 for respectively connecting the collet to the shaft 69 and to the shank of the bit to be ground, or it may be a pneumatically operated collet which is automatically opened at the end of the complete grinding cycle and is closed at the beginning of each grinding cycle.

AUTOMATIC OPERATION Referring to FIG. as well as the other FIGS. of the drawings, the switch 16 is first actuated to start the motor 13 thereby to rotate the grinding wheels 14 and 15. A control switch 80, mounted to the control box 28, is set in either the check position closing a set of contacts 80a or in the automatic position closing a set of contacts 80!). Assuming an automatic operation, with the roof bit to be sharpened locked in the collet 70, the operator closes either one of a pair of start switches 81a and 8112 respectively mounted in the control boxes 27 and 28 to initiate a complete grinding cycle. Closing of either of these switches energizes a cam switch start solenoid CS closing a set of contacts CS-l connected in series with the switch 80b and the coil of a motor control relay MCR across AC. power conductors 83 and 84. The relay MCR thus picks up to close a set of contracts MCR-l connected in the power line to the traversing motor thereby to set the traversing unit into operation. Closing of the CS-l contacts also energizes a timer motor Ml which rotates a set of switch control cams which maintain the contacts CS-l closed for one revolution of the cams. Accordingly the motor M1 is deenergized after each complete revolution of the switch control cams when the contacts CS1 open. Closing of either of the switches 81a and 81b also energizes a solenoid CV-1 which controls a valve to feed air to one of the ports 67 and 68 to rotate the shaft 69 and the bit 4 into a predetermined angular position for grinding one of the bit faces. It may be seen in FIG. 4 that the bit 24 is held at an angle of 20 relative to the plane of the wheel 15. Moreover, each time a switch 81a or 81b is closed the solenoid CTR of a counter is energized to trip the counter one unit.

A set of cam operated contacts CS-2 then close to operate the solenoid PS of a pneumatic valve (not shown) which feeds air to the forward side of the piston-cylinder 25 to drive the carriage in a rearward direction toward the grinding position thereby to press the bit against the wheel 15 as the bit is moved back and forth across the working surface of the wheel by the traversing unit 19. Air is continually applied to the rear end of the piston and control is effected by controlling the supply of air to the end thereof at the front of the machine.

The contacts CS-2 remain closed only for a sufficient time of between about onetwentieth and one second for the control valve to move into the position wherein the air is fed to the forward end of the piston-cylinder 25. The piston is thereafter held in the forward grinding position engaging the bit against the wheel 15 until a reversing signal is supplied to the control valve to vent the forward end of the cylinder.

About four to six seconds after the switch contacts CS2 open, a set of cam operated contacts CS-3 close to energize the reversing solenoid RS which operates the pneumatic control valve to vent the forward side of the piston-cylinder so that the carriage 13 moves forwardly away from the grinding position to retract the bit 24 away from the wheel 15.

A set of cam operated contacts CS-S then close to energize a solenoid CV-2 which reverses the supply of air to the ports 67 and 68 thereby to rotate the shaft 69 and the bit 24 through exactly and hold it in that position against the fixed stop in the unit 23. A set of cam operated switch contacts CS4 then close to again energize the solenoid PS to cause the carriage assembly 18 to move into a grinding position. Since the tool piece holder unit 23 operates considerably faster then the piston-cylinder assembly 25, the switch CS4 can close shortly before the switch CS5 closes thereby to speed up the operation of the machine. About four to six seconds after the solenoid PS is energized a set of cam operated switch contacts CS-6 close toenergize the return solenoid RS to retract the carriage i8 and bit 24 out of the grinding position. The contacts CS-lt then open to deenergize the timer motor M1 and drop out the relay MCR to deenergize the traversing motor 20. The operator may then remove the sharpened bit 24 from the collet 7t} and repeat the above described oper ation for the next bit to be ground.

A pair of reversing switches are respectively mounted in the switch boxes 27 and 28 and connected in circuit '5 a set of cam operated switch contacts CS7 close at about the same time as the contacts CS4 close. The contacts CS7 are serially connected with a Sensor unit 75 and the return solenoid RS so that when a pair of terminals 76a and 76b of the sensor'unit are interconnected the solenoid RS is energized toretract the carriage 18 and thus pull the bit 24 away from the grinding wheel.

' Referring to FIG. 2, a connector 77a is mounted to the frame of the machine and is connected electrically (connection not shown) to the terminal 76a of the sensor unit. A second connector 7717 is electrically connected to the terminal 76b (connection not shown) and is mounted to the rear end of a metal rod 78 slidably journaled in an insulating pillow block 79 which insulates the rod 78 from the frame of the machine.

A headed bolt 78a is threaded into the. forward end of the rod 78 and a metal arm 82 has a hole 82a through which the shank of the bolt 78a extends. The diameter of the hole 82a is substantially larger than that of the bolt shank so that there is no mutual connection between the arm 82 and the bolt 78a except at the head of the bolt. The arm 82 is fixed to and depends from the rear end of the carriage 18. I

When the carriage moves into the grinding position during the first grinding operation, the cam switch contacts CS7 being open, the arm 82 engages the front end of the rod 78 and slides it rearwardly in the block 79 to a position corresponding to the rearwardmost position of the carriage during the first grinding operation. When the carriage then retracts to permit rotation of the tool piece, the friction between the rod 78 and the block 79 holds the rod in the set position. The cam switch CS-4 closes before the arm 82 engages the head of the bolt 78a whereby the carriage then moves rearwardly for the second grinding operation. When the arm 82 engages the front end of the rod 78 the connector 77b is grounded to the frame of the machine which thus completes the electric eonnection between the sensor input terminals 76a and 76b. Since the switch CS7 is closed at this time the solenoid RS is energized to retract the carriage and complete the second grinding operation with the two cutting edges being symmetrically ground. As the carriage returns to the forwardmost position the arm 82 engages the head of the bolt 78a and resets the rod 78 in the fully forward position before the next drill bit is sharpened.

The sensor unit 75 is preferably a solid state voltage step down unit for safety reasons. However, the contacts 77a and 77b could be connected directly in series with the contacts CS7 and the solenoid RS if desired, or the unit 75 could be a transformer.

While the present invention has been described in connection with particular embodiments thereof, it will be understood by those skilled in the art that many changes and modifications may be made without departing from the true spirit and scope of the present invention. Therefore, it is intended by the appended claims to cover all such changes and modifications which come within the true spirit and scope of-the invention.

What I claim is:

1. Grinding apparatus for sharpening a tool piece having a pair of cutting edges respectively defined by first and second surfaces on the tool piece, comprising a rotatably driven grinding wheel having a peripheral grinding surface,

a carriage mounted for reciprocal, rectilinear movement toward and away from said wheel,

drive means for controllably moving said carriage in a first direction toward said wheel into a grinding position and in a second direction away from said wheel into a loading position,

reciprocal traversing means mounted by said carriage I for reciprocal movement between two set positions in a direction traverse to the direction of movement of said carriage,

a tool piece holder rotatably carried by said reciprocating means for holding the tool piece to be sharpened in each oftwo angularly displaced positions against said grinding surface when said carriage is in a grinding position, and

control means operating said drive means to move said carriage in said first direction to urge said tool piece against said grinding surface; operating said traversing means to move said tool piece back and forth between said set positions against said grinding surface to grind said first surface; then operating said drive means to retract said carriage and said tool piece away from said wheel; then causing said tool piece holder to rotate through a predeter mined angle; then operating said drive means again to move said carriage in said first direction toward said wheel to urge said second surface of said tool piece against said grinding surface; operating said traversing means to move said tool piece between said two set positions back and forth across said grinding surface to grind said second surface; and then operating said drive means to retract said carriage and said tool piece away from said wheel.

2. Grinding apparatus according to claim 1 wherein said drive means comprises fluid operated piston and cylinder means for exerting a constant pressure between said tool piece and said grinding surface when said carriage is in said grinding position.

3. Grinding apparatus according to claim 2 wherein said tool piece is a drill bit and said angle through which said tool holder is rotated 4. Grinding apparatus according to claim 1 comprising manually operated means overriding said control means to operate said driving means to retract said carriage and said tool piece away from said wheel.

5. Grinding apparatus according to claim 2 comprising means for continuously applying fluid pressure to one end of said cylinder for urging said carriage away from said wheel, and wherein the movement of said carriage is controlled by the application of fluid pressure to the other end of said cylinder.

6. Grinding apparatus according to claim 5 wherein said traversing means comprises an electric motor.

7. Grinding apparatus according to claim 2 comprisadjustment means for adjusting the lateral position of said carriage relative to said grinding wheel.

8. Grinding apparatus for sharpening a tool piece having a pair of cutting edges respectively defined by first and second surfaces on the tool piece, comprising a rotatably driven grinding wheel having a peripheral grinding surface,

a carriage mounted for reciprocal movement toward and away from said wheel,

drive means for controllably moving said carriage toward and away from said wheel,

reciprocable traversing means mounted by said carriage for reciprocal movement in a direction traverse to the direction of movement of said carriage,

a tool piece holder rotatably carried by said reciprocating means for holding the tool piece to be sharpened in each of two angularly displaced positions against said grinding surface when said carriage is in a grinding position,

control means operating said drive means to move said carriage in a forward direction to urge said tool piece against said grinding surface; operating said traversing means to move said tool piece back and forth against said grinding surface to grind said first surface; then operating said drive means to retract said carriage and said tool piece away from said wheel; then causing said tool piece holder to rotate through a predetermined angle; then operating said drive means again to move said carriage toward said wheel to urge said second surface of sensor means settable by the forward movement of said carriage during the grinding of said first surface and operable during the grinding of said second surface for moving said tool piece away from said grinding surface when said carriage has moved forwardly during the sharpening of said second surface to the forwardmost position of said carriage during the grinding of said first surface.

9. Grinding apparatus according to claim 8 wherein said sensor means comprises switch means mounted for movement by said carriage during the grinding of said first surface and operatively connected in the control circuit for said drive means.

10. Grinding apparatus according to claim 8 wherein said switch means comprises a conductive member slidably disposed in a guide means for movement along a path parallel to the reciprocatory path of said carriage,

means electrically insulating said member from said carriage,

a conductive arm extending from said carriage for engagement with one end of said member to move said arm in a rearward direction and to electrically connect said arm to said carriage, and

means on said member for engagement by said arm during the forward movement of said carriage away from said wheel to retract said member to a forward position.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,905,157 Dated September 16, 1975 Inv t fl Phillip A. Sollami It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line ll, "comprises" should be --comprise--; Column 1, line 16, "Then" should be --When--; Column 3, line 5, "to" should be --on--; Column 3, line 23, delete --a--; Column 6, line 9, "traverse" should be -transverse--; Column 7, lines 8 and 9, "traverse" should be --transverse-- Signed and Scaled this thirtieth Day of Dectmber1975 [SEAL] Attest:

RUTH c. MASON CJIAISIIAl-LDANN Arresting Officer Commission" of hunts and Trademarks 

1. Grinding apparatus for sharpening a tool piece having a pair of cutting edges respectively defined by first and second surfaces on the tool piece, comprising a rotatably driven grinding wheel having a peripheral grinding surface, a carriage mounted for reciprocal, rectilinear movement toward and away from said wheel, drive means for controllably moving said carriage in a first direction toward said wheel into a grinding position and in a second direction away from said wheel into a loading position, reciprocal traversing means mounted by said carriage for reciprocal movement between two set positions in a direction traverse to the direction of movement of said carriage, a tool piece holder rotatably carried by said reciprocating means for holding the tool piece to be sharpened in each of two angularly displaced positions against said grinding surface when said carriage is in a grinding position, and control means operating said drive means to move said carriage in said first direction to urge said tool piece against said grinding surface; operating said traversing means to move said tool piece back and forth between said set positions against said grinding surface to grind said first surface; then operating said drive means to retract said carriage and said tool piece away from said wheel; then causing said tool piece holder to rotate through a predetermined angle; then operating said drive means again to move said carriage in said first direction toward said wheel to urge said second surface of said tool piece against said grinding surface; operating said traversing means to move said tool piece between said two set positions back and forth across said grinding surface to grind said second surface; and then operating said drive means to retract said carriage and said tool piece away from said wheel.
 2. Grinding apparatus accOrding to claim 1 wherein said drive means comprises fluid operated piston and cylinder means for exerting a constant pressure between said tool piece and said grinding surface when said carriage is in said grinding position.
 3. Grinding apparatus according to claim 2 wherein said tool piece is a drill bit and said angle through which said tool holder is rotated is 180*.
 4. Grinding apparatus according to claim 1 comprising manually operated means overriding said control means to operate said driving means to retract said carriage and said tool piece away from said wheel.
 5. Grinding apparatus according to claim 2 comprising means for continuously applying fluid pressure to one end of said cylinder for urging said carriage away from said wheel, and wherein the movement of said carriage is controlled by the application of fluid pressure to the other end of said cylinder.
 6. Grinding apparatus according to claim 5 wherein said traversing means comprises an electric motor.
 7. Grinding apparatus according to claim 2 comprising adjustment means for adjusting the lateral position of said carriage relative to said grinding wheel.
 8. Grinding apparatus for sharpening a tool piece having a pair of cutting edges respectively defined by first and second surfaces on the tool piece, comprising a rotatably driven grinding wheel having a peripheral grinding surface, a carriage mounted for reciprocal movement toward and away from said wheel, drive means for controllably moving said carriage toward and away from said wheel, reciprocable traversing means mounted by said carriage for reciprocal movement in a direction traverse to the direction of movement of said carriage, a tool piece holder rotatably carried by said reciprocating means for holding the tool piece to be sharpened in each of two angularly displaced positions against said grinding surface when said carriage is in a grinding position, control means operating said drive means to move said carriage in a forward direction to urge said tool piece against said grinding surface; operating said traversing means to move said tool piece back and forth against said grinding surface to grind said first surface; then operating said drive means to retract said carriage and said tool piece away from said wheel; then causing said tool piece holder to rotate through a predetermined angle; then operating said drive means again to move said carriage toward said wheel to urge said second surface of said tool piece against said grinding surface; operating said traversing means to move said tool piece back and forth across said grinding surface to grind said second surface; and then operating said drive means to retract said carriage and said tool piece away from said wheel, and sensor means settable by the forward movement of said carriage during the grinding of said first surface and operable during the grinding of said second surface for moving said tool piece away from said grinding surface when said carriage has moved forwardly during the sharpening of said second surface to the forwardmost position of said carriage during the grinding of said first surface.
 9. Grinding apparatus according to claim 8 wherein said sensor means comprises switch means mounted for movement by said carriage during the grinding of said first surface and operatively connected in the control circuit for said drive means.
 10. Grinding apparatus according to claim 8 wherein said switch means comprises a conductive member slidably disposed in a guide means for movement along a path parallel to the reciprocatory path of said carriage, means electrically insulating said member from said carriage, a conductive arm extending from said carriage for engagement with one end of said member to move said arm in a rearward direction and to electrically connect said arm to said carriage, and means on said member for engagement by said arm during the forward movement of said carriage away from said wheel to retract said member to a forward position. 